Dahl, Mark V.

Background: Nerve involvement developed in a patient with granuloma annulare, as evidenced by a perineural infiltrate of histiocytes in the dermis. The histopathologic pattern was suggestive of leprosy. No mycobacteria were observed, and neurologic testing was normal. Objective: To determine whether inflammation of the nerves or perineural tissue is common in granuloma annulare, we studied the cutaneous nerves in skin biopsy specimens from 14 patients with granuloma annulare. Methods: Sections were stained with hematoxylin-eosin to highlight inflammatory cells and with S-100 to identify cutaneous nerves. Results: No inflammation around nerves was found in 12 specimens, abutting granulomatous inflammation was found in 1 specimen, and enveloping granulomatous inflammation was found in 1 specimen. No nerves were infiltrated by inflammatory cells. Conclusion: Perineural granulomatous inflammation resembling the perineural infiltrate of leprosy appears to be an uncommon characteristic of granuloma annulare. Clinical correlation and acid-fast stains can assist in establishing the correct diagnosis. Contexte: Une atteinte nerveuse est apparue chez un patient atteint de granulome annulaire, comme en témoignait un infiltrat périneural d'histiocytes dans le derme. Les signes histopathologiques étaient évocateurs de la lèpre, mais aucune mycobactérie n'a été observée, et l'examen neurologique était normal. Objectif: L'étude visait à déterminer si l'inflammation des nerfs ou du tissu périneural est fréquente dans le granulome annulaire; pour ce faire, nous avons examiné les nerfs cutanés dans des prélèvements biopsiques de la peau, effectués sur 14 patients atteints de granulome annulaire. Méthodes: Les coupes ont été colorées à l'hématoxyline-éosine pour mettre en évidence des cellules inflammatoires, ainsi qu'au S-100 pour repérer les nerfs cutanés. Résultats: Aucune inflammation autour des nerfs n'a été observée sur 12 prélèvements, mais il y avait présence d'inflammation granulomateuse contiguë sur un prélèvement et d'inflammation granulomateuse enveloppante, sur un autre prélèvement. Les nerfs n'ont pas été infiltrés par les cellules inflammatoires. Conclusion: L'inflammation granulomateuse périneurale qui ressemble à l'infiltration périneurale observée dans la lèpre semble un signe peu fréquent du granulome annulaire. L'établissement de corrélations cliniques et des colorations résistantes à l'acide peuvent faciliter la pose du bon diagnostic.

SummaryStem cells live long lives, renew themselves, and differentiate into more mature, less potent, specialized cells, such as epidermal keratinocytes and dermal fibroblasts. Stem cells can be embryonic, if derived from an embryo, or adult/somatic if derived from postembryonic tissue. By producing new skin cells, stem cell division and differentiation can potentially rejuvenate skin and restore hair. To reproduce, stem cells can undergo symmetric nondifferentiative or differentiative divisions, or asymmetric differentiative divisions. Asymmetric divisions reproduce the stem cell and provide a more differentiated, but less potent transient amplifying cell. Divisions and differentiation of transient amplifying cells regenerate tissues by producing cells of a specific lineage, for example, keratinocytes. Epidermal stem cells lie in niches in the interfollicular epidermis, sebaceous gland, and in the bulge regions of hair follicles. These epidermal stem cells renew the epidermis, the sebaceous glands, and hair follicles after mature cells die. Dermal stem cells lie in the hair papillae, around pericytes, and elsewhere among other dermal cells. These form pericytes, myoblasts, fibroblasts, chondrocytes, and other specialized dermal cells. Along with other signaling pathways, the Wnt signaling pathway controls stem cell fate. Wnt signals enlist two functionally and chemically different gene coactivators to direct the time and type of replicative divisions. Stem cells may help to heal wounds, repair damaged tissues, regenerate aged skin, and reinvigorate growth of skin, hair, nails, and mucous membranes.